Such a switching power-supply device performing a control of an output 15 voltage by switching operation includes a switching element connected in series with an input power source and a primary winding of a transformer, and a switching control circuit for performing on-and-off control of the switching element to switch operation thereof, and the switching power-supply device is configured to rectify and smooth a secondary electromotive force generated by a secondary winding of the transformer and thus to output a direct voltage.
Also, a switching power-supply device in which an integrated circuit is provided separate from a switching element to control the switching element is described in JP 2008-211881 A.